The present invention relates to an automatic vehicular velocity controlling system and method having such an inter-vehicle distance controlling function as controlling a vehicular velocity to maintain an appropriate inter-vehicle distance.
An European Patent Application First Publication No. EP 0 982 172 A2 published on Mar. 1, 2000 exemplifies a previously proposed automatic vehicular velocity controlling system. (A U.S. Pat. No. 5,959,572 issued on Sep. 28, 1999 also exemplifies another previously proposed automatic vehicular velocity controlling system.)
In such a previously proposed automatic vehicular velocity controlling systems as described in the above-described European Patent Application First Publication, a response characteristic of a feedback inter-vehicle distance control system is determined in accordance with a relative velocity of an automotive vehicle in which the above-described vehicular velocity controlling system is mounted (hereinafter, also referred to as a host vehicle) to a preceding vehicle which is running ahead of the vehicle. Such an inter-vehicle distance control system as described above has aimed at providing a sharp response to a variation in the relative velocity by enlarging feedback constants when the magnitude of the relative velocity is large.
In addition, in such a previously proposed automatic vehicular velocity controlling system as described above, a deviation from a dynamic characteristic of an object to be controlled is estimated (so-called, external disturbance estimation) and an added value of an external disturbance to a target vehicular velocity is determined to be a new target vehicular velocity so that the inter-vehicle distance control is carried out in accordance with the external disturbance value (a running resistance or so forth).
Furthermore, in the above-described previously proposed automatic vehicular velocity controlling system, if a time duration from a time at which the preceding vehicle is stopped to a time at which the host vehicle has reached to the preceding vehicle at the present vehicular velocity of the host vehicle is defined as an inter-vehicle time duration, a target inter-vehicle distance is defined as a product between a velocity of the preceding vehicle and the inter-vehicle time duration.
In this case, the setting of inter-vehicle time duration is carried out by a vehicular occupant""s manipulation on a three-stage changeover switch which switches the inter-vehicle time duration into a remote (long) distance, a middle distance, and a close (short) distance.
There are various methods of deriving the relative velocity used in the inter-vehicle distance control. One of the methods include detecting the inter-vehicle distance and deriving the relative velocity from a variation of the detected inter-vehicle distance.
However, an error in a detection of the inter-vehicle distance causes an occurrence of an error in the relative velocity. As the inter-vehicle distance becomes longer, the error tends to be increasingly included in the relative velocity. Hence, even in an actual case where the distance from the preceding vehicle becomes remote and the relative velocity is small, it is recognized that the error in the detection of the inter-vehicle distance causes the relative velocity to be changed to tend to become large. At this time, the feedback response characteristic is caused to become quick and a sharp control is resulted. Therefore, an unmatched feeling to a driving sense may be given to a vehicular occupant of the host vehicle.
It is noted that even in a case of a direct detection of the relative velocity, the error of calculation to detect the relative velocity occurs and, therefore, the unmatched feeling to the driving sense may be given to the occupant in the similar way as described above.
In addition, in a case where another vehicle which is running at a slightly slower velocity than the host vehicle is interrupted in front of the host vehicle, the relative velocity is small so that a feedback response is slow.
Hence, a control response is delayed and the host vehicle becomes remote from the preceding vehicle with a large delay to maintain a predetermined inter-vehicle distance form the interrupted other vehicle. Consequently, the unmatched feeling to the driving sense is given by the vehicular occupant.
Next, since the external estimation is the detection of the deviation of the external disturbance from the normal dynamic characteristic of the object to be controlled (i.e., the host vehicle), the deviation of the external disturbance from the normal dynamic characteristic of the object to be controlled (the normal dynamic characteristic is found during a flat road run of the vehicle) continuously occurs during a ascending slope run of the vehicle. Hence, the deviation is continuously added to the target vehicular velocity so that the vehicle (host vehicle) is continuously controlled to be accelerated. In this case, when the host vehicle has caught up with the preceding vehicle and the inter-vehicle distance has reached to a set value of inter-vehicle distance, the target vehicular velocity of the host vehicle is changed to the target vehicular velocity of the host vehicle is changed to a deceleration direction. However, since the above-described deviation is continued to be added, a start of deceleration is delayed so that the host vehicle becomes approached excessively to the preceding vehicle. This phenomenon also gives the vehicular occupant the unmatched feeling to the driving sense.
Next, suppose that the vehicular driver tries to widen the inter-vehicle distance and modifies the inter-vehicle time duration to a large value (for example, from the close distance to the remote distance) in a case where the host vehicle is running to follow the preceding vehicle at a small relative velocity to the preceding vehicle, for example, like such a case that the host vehicle is running at a substantially constant inter-vehicle distance to the preceding vehicle. In this modification of the inter-vehicle time duration, the relative velocity becomes gradually large but the response of the vehicular velocity variation to this modification is not favorable since the response characteristic is set slowly due to the small relative velocity. The above-described situation is found in such a case that the driver feels for the host vehicle to approach excessively to the preceding vehicle and manipulates the three-stage changeover switch to try to widen the inter-vehicle distance. Hence, if the vehicular velocity variation is dull upon the driver""s manipulation on the three-stage changeover switch, the driver does not feel that the three-stage changeover switch has been operated to widen the inter-vehicle distance but gives the unmatched feeling to the driving sense.
With the above-described problems in mind, it is an object of the present invention to provide automatic vehicular velocity controlling system and method for an automotive vehicle which are capable of performing an appropriate inter-vehicle distance control with an appropriate response characteristic which accords with a vehicular running situation and without giving a driver""s unmatched feeling to the driving sense.
According to one aspect of the present invention, there is provided an automatic vehicular velocity controlling system for an automotive vehicle, comprising: an inter-vehicle distance detector to detect an inter-vehicle distance from the vehicle to a preceding vehicle which is running ahead of the vehicle; a vehicular velocity detector to detect a vehicular velocity of the vehicle; a relative velocity detector to detect a relative velocity of the vehicle to the preceding vehicle; an inter-vehicle distance command value calculating section that calculates a command value of the inter-vehicle distance; a control response characteristic determining section that determines a response characteristic of an inter-vehicle related feedback control system in accordance with the relative velocity; a response characteristic correcting section that corrects the response characteristic of the inter-vehicle related feedback control system determined by the control response characteristic determining section in accordance with at least the inter-vehicle distance detected by the inter-vehicle distance detector; a vehicular velocity command value calculating section that calculates an inter-vehicle related controlling vehicular velocity command value on the basis of the response characteristic of the inter-vehicle related feedback control system corrected by the response characteristic correcting section; and a vehicular velocity controlling section that controls at least one of a driving force of the vehicle, a braking force of the vehicle, and a speed ratio of a transmission in such a manner that the vehicular velocity detected by the vehicular velocity detector is made substantially equal to the vehicular velocity command value.
According to another aspect of the present invention, there is provided an automatic vehicular velocity controlling method for an automotive vehicle, comprising: detecting an inter-vehicle distance from the vehicle to a preceding vehicle which is running ahead of the vehicle; detecting a vehicular velocity of the vehicle; detecting a relative velocity of the vehicle to the preceding vehicle; calculating a command value of the inter-vehicle distance; determining a response characteristic of an inter-vehicle related feedback control system in accordance with the relative velocity; correcting the determined response characteristic of the inter-vehicle related feedback control system in accordance with at least the detected inter-vehicle distance; calculating an inter-vehicle related controlling vehicular velocity command value on the basis of the corrected response characteristic of the inter-vehicle related feedback control system; and controlling at least one of a driving force of the vehicle, a braking force of the vehicle, and a speed ratio of a transmission in such a manner that the detected vehicular velocity is made substantially equal to the vehicular velocity command value.
This disclosure of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.